1. Field of the Invention
The present invention relates to a power generation controller for controlling a generator in accordance with a control command transmitted from an external control unit.
2. Description of Related Art
It is known to regulate an output voltage of a vehicle generator driven by an engine mounted on a vehicle by use of a power generation voltage controller as disclosed in Japanese Patent Application Laid-open No. 8-275407. Such a power generation voltage controller includes a signal discriminating means connected to an engine ECU (Electronic Control Unit), a power generation voltage setting means, a voltage controlling comparator, and an excitation current controlling transistor connected to an excitation winding of a vehicle generator.
The engine ECU transmits, as a vehicle state signal containing a traveling state signal etc., a binary pulse train signal to the power generation voltage controller. The binary pulse train signal transmitted from the engine ECU is decoded into a traveling state signal etc. by the signal discriminating means of the power generation voltage controller. The signal discriminating means holds the decoded traveling state signal etc. until it next receives the vehicle state signal. The power generation voltage setting means determines a target power generation voltage on the basis of the traveling state signal etc. held in the signal discriminating means. The determined target power generation voltage is compared with a battery voltage in the voltage controlling comparator. The excitation current controlling transistor is on/off controlled in accordance with the comparison results in the voltage controlling comparator to control the flow of the excitation current.
Generally, the vehicle generator is located, together with the power generation voltage controller, in the vicinity of the vehicle engine which drives the vehicle generator. Accordingly, there has been a possibility that noise which the vehicle engine emits from its ignition device is incorporated into the binary pulse train signal transmitted from the engine ECU to the power generation voltage controller.
It is possible to detect incorporation of the noise into the binary pulse train signal, if the pulse width of the binary pulse train signal is changed by the incorporation of the noise. However, since the power generation voltage controller cannot continue to perform the control operation on the basis of the binary pulse train signal including error, it is necessary for the power generation voltage controller to perform the control operation on the basis of the previously received binary pulse train signal, or to change to internal control mode when the power generation voltage controller detects error in the received binary pulse train signal. This prevents the power generation voltage controller from performing optimum control.
Furthermore, in a case where error in the binary pulse train signal due to the noise cannot be detected, there is a problem in that the power generation voltage controller erroneoulsy controls the vehicle generator at least until it next receives the binary pulse train signal.